The story of young engineers who resurrected an engine nearly twice their age.

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There has never been anything like the Saturn V, the launch vehicle that powered the United States past the Soviet Union to a series of manned lunar landings in the late 1960s and early 1970s. The rocket redefined "massive," standing 363 feet (110 meters) in height and producing a ludicrous 7.68 million pounds (34 meganewtons) of thrust from the five monstrous, kerosene-gulping Rocketdyne F-1 rocket engines that made up its first stage.

At the time, the F-1 was the largest and most powerful liquid-fueled engine ever constructed; even today, its design remains unmatched (though see the sidebar, "The Soviets," for more information on engines that have rivaled the F-1). The power generated by five of these engines was best conceptualized by author David Woods in his book How Apollo Flew to the Moon—"[T]he power output of the Saturn first stage was 60 gigawatts. This happens to be very similar to the peak electricity demand of the United Kingdom."

Despite the stunning success of the Saturn V, NASA's direction shifted after Project Apollo's conclusion; the Space Transport System—the Space Shuttle and its associated hardware—was instead designed with wildly different engines. For thirty years, NASA's astronaut corps rode into orbit aboard Space Shuttles powered by RS-25 liquid hydrogen-powered engines and solid-propellant boosters. With the Shuttle's discontinuation, NASA is currently hitching space rides with the Russians.

But there's a chance that in the near future, a giant rocket powered by updated F-1 engines might once again thunder into the sky. And it's due in no small part to a group of young and talented NASA engineers in Huntsville, Alabama, who wanted to learn from the past by taking priceless museum relics apart... and setting them on fire.

Enlarge/ An F-1 engine on display at NASA's Marshall Space Flight Center. Author's wife at right for scale.

Lee Hutchinson

Enter our young rocket scientists

Tom Williams is the kind of boss you want to have. He's smart, of course—that's a prerequisite for his job as the director of the NASA Marshall Space Flight Center's (MSFC) Propulsion Systems Department. But he doesn't mind stepping back and giving his team interesting challenges and then turning them loose to work out the details. Case in point: NASA's Space Launch System (SLS), intended to be an enormous heavy-lift system that will rival the Saturn V in size and capabilities. In thinking about propulsion for the SLS, NASA for the first time in thirty years is considering something other than solid rocket boosters.

The decision to use a pair of solid rocket boosters for the Space Shuttle instead of liquid-fueled engines like the F-1 had been partly technical and partly political. Solid fuels are hugely energy dense and provide an excellent kick to get a spacecraft moving off of the ground; also, selecting solid fuel boosters allowed the government to send some available contracting dollars to companies involved with building intercontinental ballistic missiles, leveraging that expertise and providing those companies with additional work.

The Soviets

The closest thing the Saturn V had to a contemporary was the Soviet N1, which launched four times and exploded each time, almost always because of failures in the complex system that managed the N1's 30 individual first-stage rocket motors. In contrast, the Saturn V has an unblemished string of successful launches, never suffering a problem or failure significant enough to trigger an abort.

Though the F-1 was the largest and most powerful single-chamber liquid-fueled rocket engine ever successfully flown, its power was exceeded by a pair of Soviet designs. The RD-170 engine (used for the only two launches of the Energia rocket) and its RD-171 variant (used on the Zenit rocket) both produce more thrust, but the Soviets were unable to overcome problems with combustion instability in a large rocket's nozzle. Combustion instability is the tendency of the burning propellent to swirl as it is pumped into the nozzle; as we'll see, NASA eventually developed a series of baffles on the F-1's injector plate to damp its instability. The Soviet Union chose to work around the problem by fitting the RD-170 with four separate nozzles instead of one large one, giving the RD-170 and -171 the visual appearance of being four separate engines.

This workaround came to be not because the Soviets were lesser engineers or scientists—the Soviet space program was filled with brilliant, talented people—but instead because for most of its existence the Soviet space program's various rocket design bureaus were caught in a push-pull war of direction and leadership between two chief designers: Sergei Korolev and Valentin Glushko. Korolev favored cryogenically fueled rockets, and Glushko favored those powered by hypergolic propellants. This split in rocket strategy sapped resources, preventing the full force of Soviet engineering talent from focusing on either and ultimately stunting their rocketry program.

For more information on the clashes between Korolev and Glushko, see Asif Siddiqi's Challenge to Apollo (also available in twoparts from various places). It is the definitive work on the history of the fascinating and curiously fragmented Soviet space program.

But solid boosters have several downsides, including an inability to stop combustion. Without pumps to switch off or valves to close, solid boosters work a lot like the "morning glory" sparklers my dad used to buy on the Fourth of July—once lit, they burn until they're done. Solid rocket booster design decisions, specifically in regard to containing combustion, contributed to the destruction of the Space Shuttle Challenger and the death of its crew (though Challenger's destruction was more a failure of NASA management than of technology).

Still, as the Space Shuttle program drew to a close and potentialsuccessors came and went, the inertia of solid boosters and the facilities and people that produced them ensured that they remained a part of the plans.

SLS gave NASA the chance to do a total rethink. As design studies got underway, Williams realized it might be a good idea to re-familiarize the MSFC Propulsion Systems Department with huge kerosene gas generator engines like the F-1 (referred to in shorthand as "LOX/RP-1" or just "LOX/RP" engines, after their oxidizer and fuel mixture of liquid oxygen and RP-1 kerosene). Scale aside, the F-1 is conceptually a relatively simple design, and that simplicity could translate into cost reduction. Reducing cost for space access is a key priority—perhaps even the overriding priority—outside of safety.

There was a problem, though. SLS' design parameters called for a Saturn V-scale vehicle, capable of lifting 150 metric tons into low Earth orbit. No one working at MSFC had any real experience with gigantic LOX/RP-1 engines; nothing in the world-wide inventory of launch vehicles still operates at that scale today. So how do you make yourself an expert in tech no one fully understands?

Nick Case and Erin Betts, two liquid engine systems engineers working for Williams, found a way. Although no launch vehicles that used F-1 engines are still around, actual F-1s do exist. Fifteen examples sit attached to the three Saturn V stacks on display at NASA facilities, including MSFC; dozens more are scattered around the country on display or in storage. Williams' team inspected the available engines and soon found their target: a flight-ready F-1 which had been swapped out from the launch vehicle destined for the to-be-canceled Apollo 19 mission and instead held in storage for decades. It was in excellent condition.

Case and Betts spearheaded the paperwork-intensive effort to requisition the F-1 from storage and get it into their workshop. They were aided by R.H. Coates, a more senior member of Williams' team and lead propulsion engineer for the SLS Advanced Development Office. Williams offered encouragement and assistance from the management side, but the team was otherwise given free rein on how to proceed. After some study, they came to Williams with a request that was pure engineer: "Why don't we just go ahead and take this thing apart and see what makes it work?"

Williams said yes. "It allowed some of our young engineers to get some hands-on experience with the hardware," he told me, "what we would term the 'dirty hands' approach to learning, just like you did when you took apart your bicycle when you were a kid, or your dad's lawnmower or his radio. One of the best ways to learn as an engineer, or in anything, is to take it apart, study it, ask questions."

And then, hopefully, build a better one.

The plans! The plans!

The F-1 teardown started in relatively low-key fashion. As the team dug into the engine, it became obvious that the internal components were in good shape. In fact, though there was some evidence of rainwater damage, the engine overall was in great shape.

The team initially wanted to build an accurate computer model of every component in the engine so that its behavior could be modeled and simulated, but another goal soon began to take shape: maybe, just maybe, they could mount some of the engine components on a test stand and make the F-1 speak again after 40 years.

Why was NASA working with ancient engines instead of building a new F-1 or a full Saturn V? One urban legend holds that key "plans" or "blueprints" were disposed of long ago through carelessness or bureaucratic oversight. Nothing could be further from the truth; every scrap of documentation produced during Project Apollo, including the design documents for the Saturn V and the F-1 engines, remains on file. If re-creating the F-1 engine were simply a matter of cribbing from some 1960s blueprints, NASA would have already done so.

A typical design document for something like the F-1, though, was produced under intense deadline pressure and lacked even the barest forms of computerized design aids. Such a document simply cannot tell the entire story of the hardware. Each F-1 engine was uniquely built by hand, and each has its own undocumented quirks. In addition, the design process used in the 1960s was necessarily iterative: engineers would design a component, fabricate it, test it, and see how it performed. Then they would modify the design, build the new version, and test it again. This would continue until the design was "good enough."

Further, although the principles behind the F-1 are well known, some aspects of its operation simply weren't fully understood at the time. The thrust instability problem is a perfect example. As the F-1 was being built, early examples tended to explode on the test stand. Repeated testing revealed that the problem was caused by the burning plume of propellent rotating as it combusted in the nozzle. These rotations would increase in speed until they were happening thousands of times per second, causing violent oscillations in the thrust that eventually blew the engine apart. The problem could have derailed the Saturn program and jeopardized President Kennedy's Moon landing deadline, but engineers eventually used a set of stubby barriers (baffles) sticking up from the big hole-riddled plate that sprayed fuel and liquid oxygen into the combustion chamber (the "injector plate"). These baffles damped down the oscillation to acceptable levels, but no one knew if the exact layout was optimal.

Enlarge/ Detail on an F-1 engine injector plate at the forward end of the nozzle. Fuel and liquid oxygen are sprayed out of these holes under tremendous pressure, with each ring alternating propellant and oxidizer. Photo is from F-1 engine number F-6045, on public display at the US Space and Rocket Center in Huntsville.

Lee Hutchinson

The baffle arrangement "was just a trial and error thing," explained Senior Propulsion Engineer R.H. Coates. "But we'd like to model that and say, well, what if you took one of those baffles out?" Because the baffles are mounted directly to the injector plate, they take up surface area that would otherwise be occupied by more injector holes spraying more fuel and oxidizer; therefore, they rob the engine of power. "So if you want to up the performance on this thing, we can evaluate that with modern analytical techniques and see what that does to your combustion stability."

But before any "hot-fire" testing could occur, the team had to take the very physically real F-1 engine and somehow model it. It's easy—well, relatively easy—to turn a set of CAD files into a real product. Turning a real product into a set of CAD files, though, requires a bit of ingenuity, especially when that product is a gigantic rocket engine.

To tackle the task, NASA brought in a company called Shape Fidelity, which specializes in a technique called "structured light scanning." If you don't have access to the laser from TRON, structured light scanning is just about the next best way to cram something inside of a computer.

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Lee Hutchinson
Lee is the Senior Technology Editor at Ars and oversees gadget, automotive, IT, and gaming/culture content. He also knows stuff about enterprise storage, security, and human space flight. Lee is based in Houston, TX. Emaillee.hutchinson@arstechnica.com

202 Reader Comments

Williams said yes. "It allowed some of our young engineers to get some hands-on experience with the hardware," he told me, "what we would term the 'dirty hands' approach to learning, just like you did when you took apart your bicycle when you were a kid, or your dad's lawnmower or his radio. One of the best ways to learn as an engineer, or in anything, is to take it apart, study it, ask questions."

I was a little depressed about our reliance on the Russians for rides to the ISS, especially because I had to tell my five year old son that no, he would not be flying the Space Shuttle, because they wouldn't be flying again. Ever.

How awesome it is that I can show him this, and get him thinking about taking a ride on an F-1B powered rocket instead! Thanks for this.

I remember seeing one of these engines at the Smithsonian back when they were still in use. They had one full engine and one quarter (cut-away) engine set against two large mirrors positioned at right angles to provide the illusion that there were five engines total. The visual effect was that of looking at the business end of the V-5. Everything else was matte black.

Other than an information plaque off to the side there were only three words written in white against the black background: Go Baby, Go!

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

Scanning a small object with the structured light scanner. The alternating horizontal bars in the purple projection are used by the cameras to detect surface detail.

What alternating horizontal bars? I don't see any.

Quote:

The gas generator spoke with a deep rumbling, topped with a rocket's crackle-crackle-crackle—a sound I'd always thought was just the microphone clipping when listening to recordings of rocket launches.

[Coates said]," but it was just a small group of engineers who got the idea to get their hands dirty."

It's a nice, simple story for a general media, and one often told by managers, but reality is rarely that clean. More often there are competing ideas, conflicts, debates and sometimes, everyone eventually agrees to go do one thing. Honestly, those debates can be just as interesting as the work that gets done.

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

I can imagine they will be declared as dual use sensitive and locked away. With a citation to North Korea having access to the full design schematics for a high performance rocket engine as to why it is being hidden away.

They're kinda hard to see in the small version of the pic, but they were pretty clear when actually looking at the thing with my eyes. They also show up OK in the full-res version. They're not black bars--more like alternating lighter purple and darker purple.

Quote:

Quote:

The gas generator spoke with a deep rumbling, topped with a rocket's crackle-crackle-crackle—a sound I'd always thought was just the microphone clipping when listening to recordings of rocket launches.

That was the auditory detail I noticed most in the one shuttle launch I was lucky enough to attend (STS-130). The shuttle stack very distinctly went crackle-crackle-crackle, just like in audio recordings. The GG did the same thing (though less loudly).

Predictive Quote: "I was a little depressed about our reliance on the Russians for rides to the ISS."

Don't be a bigot. Spaceflight is a human endeavor, it's the politics that turn it into a circle jerk.

It's not that it's Russia, or any other state. It's that a nation of our vast resources has made space exploration such a low priority, we are forced to rely upon the goodwill of others to do what we could ourselves, were it not for the politics.

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

I can imagine they will be declared as dual use sensitive and locked away. With a citation to North Korea having access to the full design schematics for a high performance rocket engine as to why it is being hidden away.

That horse may already left the stable. There a plenty of other nation-states that would like such. Anyway the requirements for an ICBM are different than going up into space.

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

I can imagine they will be declared as dual use sensitive and locked away. With a citation to North Korea having access to the full design schematics for a high performance rocket engine as to why it is being hidden away.

That horse may already left the stable. There a plenty of other nation-states that would like such. Anyway the requirements for an ICBM are different than going up into space.

Very true liquid-fueled is just a serious PITA to maintain. Are there proper solid-fuel ICBMs?

Wonderful article. This is what keeps Ars-Technica head & shoulders above the competition. I'll never stop being amazed at the engineering marvels that the Space Program produced. Glad to see that the hard-earned knowledge of the Apollo Program has yet another chance to be used again. Great stuff!

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

Nothing to really add to this wonderful bit, except that I really, really hope they make their final CAD files available Do I *need* complete CAD renderings of an F1 engine? Probably not, but I really want them.

I can imagine they will be declared as dual use sensitive and locked away. With a citation to North Korea having access to the full design schematics for a high performance rocket engine as to why it is being hidden away.

That horse may already left the stable. There a plenty of other nation-states that would like such. Anyway the requirements for an ICBM are different than going up into space.

Very true liquid-fueled is just a serious PITA to maintain. Are there proper solid-fuel ICBMs?

Small correction:Stennis Space Center is in Mississippi, not Florida. Kennedy is in Florida.

Stennis is still far enough into the swamps you might be able to run tests there. And Kennedy is obviously used for large launches still.. but Stennis is one of the locations that stuff was originally tested too.

it would be worth mentioning that the brilliant 1982 documentary Koyaanisqatsi, known for its musical score by Philip Glass and lack of commentary has close up, slow motion footage of a Saturn V rocket on launch in the opening scene.

If you liked this then try reading "Rocket Boys" by Homer Hickham - one of my favourite books of all time (which the movie 'October Sky' was based on). Great true story about a bunch of school kids in the 60's inspired by the space race to take up model rocketry.

(Google tells me they've now renamed the book 'October Sky' after the success of the movie)

We didn't actually put that much energy into it...RP-1 is just a high grade of kerosene, and the LOX was liquefied from the air. The energy content came from ancient plankton and green plants. The power output is due to the fact that you're burning the stuff with pure, dense liquid oxygen being forcibly pumped into the combustion chamber at a mindboggling rate rather than diluted, low density atmospheric oxygen.

The PEPCON explosion was at a plant producing propellant for solid rockets like the Space Shuttle boosters. It's not that the energy release was any higher...solids are actually heavy and low energy density. However, with solid rockets you can't wait to mix the oxidizer and fuel until they're in the combustion chamber, and choices for useful solid oxidizers are limited...the ammonium perchlorate oxidizer used in the Shuttle SRBs is prone to exploding on its own when mistreated. After a SRB failure (of a completely different nature...O-ring failure) destroyed Challenger, launches were frozen and the PEPCON site accumulated ~4500 tons of ammonium perchlorate.

Urban legend or not the "NASA lost the blueprints for Saturn V/Apollo" story still grimy amuses me, as do the excuses about the non computerised plans.

Back when I went to school we were taught that the purpose of technical drawing (and we only used pen, paper and various rulers etc not computers back then) was to allow any engineer to be able to create a workable, finished product from the plans.

Such plans and documentation have worked just fine ever since the industrial revolution got underway. NASA seems to be the only entity in existance incapable of getting this simple principle to work.

The team was able to use the structured light scan of that particular bolt and, in less than half a day, to fabricate a tool using an additive manufacturing method called electron beam melting to quickly "print" 3D projects out of metal powder.

Imagine you're a Rocketdyne engineer in the 60's and one day, some guy walks out of a time warp into your assembly area, pulls out some weird looking cameras, takes a few pictures of your engine, plugs some cables into some unknown equipment, and then, looking bored, sits down and directs his attention to a thin metal and glass slab for a while. When a light changes on the unknown equipment, the guy gets up, sticks his hand inside, and pulls out a tool which takes apart your engine.

That would be magic. You'd think the guy was from the 25th century or something. But no, only 45 years.

Amazing what can be forgotten in 45 years, but even more amazing is the ingenuity of relearning how to make something forgotten. Reminds me of the history channel (when it shows history) and recreating sunken boats from the Greek and Roman eras.

see Asif Siddiqi's Challenge to Apollo (also available in two parts from various places). It is the definitive work on the history of the fascinating and curiously fragmented Soviet space program.

Just started reading it and it's amazing. Shared on FB!

A short excerpt from just Chapter 1 for those hear who haven't already downloaded it:

In the Western historiography of the early history of astronautics, Tsiolkovskiy's name is the best known. But within Russia and later the Soviet Union, there were two other remarkable visionaries… One of these was Yuriy Vasilyevich Kondratyuk, a man who had a life as amazing as any figure in the history of Soviet rocketry.

He was born Aleksandr Ignatyevich Shargey in 1897 in the Ukraine. Brilliant even in his childhood, he published his seminal works in his twenties and thirties, the first, To Those Who Will Read in Order to Build, in 1919 and the second, The Conquest at Interplanetary Space, in 1929. Among the topics he described were minimum-energy spaceflight trajectories to other planets, the theory of multistage rockets, intermediate interplanetary ship refueling bases, and the landing of probes on planets using atmospheric drag. One of his most famous contributions to the literature was the formulation of a mission profile for a lunar landing using two separate vehicles, a mother ship in lunar orbit, and a lander on the surface. When American astronauts landed on the Moon in 1969, they used very much the same idea.

Shargey's career was cut short by the strangest of circumstances. In 1916, he had been conscripted into the Army to fight on the Caucasus front in Turkey. After the Bolsheviks came to power in October 1917, Shargey decided to leave the Army, but on his journey back home, he was conscripted by the rebel White Army to fight the communists, He eventually deserted but was found by the White Army again in Kiev, where he joined their ranks briefly before deserting again. After the Revolution, he was in a difficult position. To the Whites, he was a habitual deserter, and to the Reds, he was an officer in the White Army--both sides wanted him shot. To save his life, his stepmother sent him some documents of a man named Yuriy Vasilyevich Kondratyuk, who was born in 1900 and died on March I, 192I, of tuberculosis. On August 15 of the same year, Shargey assumed his new identity and tried to lead an inconspicuous life, far from the public eye. He died sometime later in 1942, defending Moscow from the Nazis. His grave was never found...